Work supported by this grant in the first six months led to advances in the understanding of the thymic role in oncogenesis and provided evidence: A. that early thymectomy may have a major protective role against the increased risk of oncogenesis in myasthenic patients since it leads to earlier remissions. B. that transcervical thymectomy is as effective in the control of myasthenia gravis and should therefore be as effective in reducing the increased cancer risk as transthoracic approaches. C. that prognosis in patients with breast cancer is dependent on the pretreatment numbers of peripheral lymphocytes and that there is an association between lymphocytes and CEA. D. that there is a significant association between peripheral lymphocytes and CEA in patients with myasthenia gravis and in other non- neoplastic diseases with high cancer risk, and that following thymectomy in mysasthenic patients lymphocyte counts increase and CEA titers decrease. These changes correspond to the reported post-thymectomy decrease in cancer risk in these patients. E. that CEA, peripheral lymphocytes and plasma androgen sulfates used in conjunction may identify patients that are at a high risk for the development of breast cancer. The details of these studies have been reported in various publications. In addition evidence has been accumulated and is to be reported that the risk of cancer in myasthenia is proportionate to the severity of disease and that post-thymectomy decreases correspond to clinical improvement.